java实现RSA加密和解密详解编程语言

RSAUtils.java

package yyy.test.rsa; 
 
import java.math.BigInteger; 
import java.security.KeyFactory; 
import java.security.KeyPair; 
import java.security.KeyPairGenerator; 
import java.security.NoSuchAlgorithmException; 
import java.security.interfaces.RSAPrivateKey; 
import java.security.interfaces.RSAPublicKey; 
import java.security.spec.RSAPrivateKeySpec; 
import java.security.spec.RSAPublicKeySpec; 
import java.util.HashMap; 
 
import javax.crypto.Cipher; 
 
public class RSAUtils { 
 
	/** 
	 * 生成公钥和私钥 
	 * @throws NoSuchAlgorithmException  
	 * 
	 */ 
	public static HashMap<String, Object> getKeys() throws NoSuchAlgorithmException{ 
		HashMap<String, Object> map = new HashMap<String, Object>(); 
		KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA"); 
        keyPairGen.initialize(1024); 
        KeyPair keyPair = keyPairGen.generateKeyPair(); 
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); 
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); 
        map.put("public", publicKey); 
        map.put("private", privateKey); 
        return map; 
	} 
	/** 
	 * 使用模和指数生成RSA公钥 
	 * 注意：【此代码用了默认补位方式，为RSA/None/PKCS1Padding，不同JDK默认的补位方式可能不同，如Android默认是RSA 
	 * /None/NoPadding】 
	 *  
	 * @param modulus 
	 *            模 
	 * @param exponent 
	 *            指数 
	 * @return 
	 */ 
	public static RSAPublicKey getPublicKey(String modulus, String exponent) { 
		try { 
			BigInteger b1 = new BigInteger(modulus); 
			BigInteger b2 = new BigInteger(exponent); 
			KeyFactory keyFactory = KeyFactory.getInstance("RSA"); 
			RSAPublicKeySpec keySpec = new RSAPublicKeySpec(b1, b2); 
			return (RSAPublicKey) keyFactory.generatePublic(keySpec); 
		} catch (Exception e) { 
			e.printStackTrace(); 
			return null; 
		} 
	} 
 
	/** 
	 * 使用模和指数生成RSA私钥 
	 * 注意：【此代码用了默认补位方式，为RSA/None/PKCS1Padding，不同JDK默认的补位方式可能不同，如Android默认是RSA 
	 * /None/NoPadding】 
	 *  
	 * @param modulus 
	 *            模 
	 * @param exponent 
	 *            指数 
	 * @return 
	 */ 
	public static RSAPrivateKey getPrivateKey(String modulus, String exponent) { 
		try { 
			BigInteger b1 = new BigInteger(modulus); 
			BigInteger b2 = new BigInteger(exponent); 
			KeyFactory keyFactory = KeyFactory.getInstance("RSA"); 
			RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(b1, b2); 
			return (RSAPrivateKey) keyFactory.generatePrivate(keySpec); 
		} catch (Exception e) { 
			e.printStackTrace(); 
			return null; 
		} 
	} 
 
	/** 
	 * 公钥加密 
	 *  
	 * @param data 
	 * @param publicKey 
	 * @return 
	 * @throws Exception 
	 */ 
	public static String encryptByPublicKey(String data, RSAPublicKey publicKey) 
			throws Exception { 
		Cipher cipher = Cipher.getInstance("RSA"); 
		cipher.init(Cipher.ENCRYPT_MODE, publicKey); 
		// 模长 
		int key_len = publicKey.getModulus().bitLength() / 8; 
		// 加密数据长度 <= 模长-11 
		String[] datas = splitString(data, key_len - 11); 
		String mi = ""; 
		//如果明文长度大于模长-11则要分组加密 
		for (String s : datas) { 
			mi += bcd2Str(cipher.doFinal(s.getBytes())); 
		} 
		return mi; 
	} 
 
	/** 
	 * 私钥解密 
	 *  
	 * @param data 
	 * @param privateKey 
	 * @return 
	 * @throws Exception 
	 */ 
	public static String decryptByPrivateKey(String data, RSAPrivateKey privateKey) 
			throws Exception { 
		Cipher cipher = Cipher.getInstance("RSA"); 
		cipher.init(Cipher.DECRYPT_MODE, privateKey); 
		//模长 
		int key_len = privateKey.getModulus().bitLength() / 8; 
		byte[] bytes = data.getBytes(); 
		byte[] bcd = ASCII_To_BCD(bytes, bytes.length); 
		System.err.println(bcd.length); 
		//如果密文长度大于模长则要分组解密 
		String ming = ""; 
		byte[][] arrays = splitArray(bcd, key_len); 
		for(byte[] arr : arrays){ 
			ming += new String(cipher.doFinal(arr)); 
		} 
		return ming; 
	} 
	/** 
	 * ASCII码转BCD码 
	 *  
	 */ 
	public static byte[] ASCII_To_BCD(byte[] ascii, int asc_len) { 
		byte[] bcd = new byte[asc_len / 2]; 
		int j = 0; 
		for (int i = 0; i < (asc_len + 1) / 2; i++) { 
			bcd[i] = asc_to_bcd(ascii[j++]); 
			bcd[i] = (byte) (((j >= asc_len) ? 0x00 : asc_to_bcd(ascii[j++])) + (bcd[i] << 4)); 
		} 
		return bcd; 
	} 
	public static byte asc_to_bcd(byte asc) { 
		byte bcd; 
 
		if ((asc >= '0') && (asc <= '9')) 
			bcd = (byte) (asc - '0'); 
		else if ((asc >= 'A') && (asc <= 'F')) 
			bcd = (byte) (asc - 'A' + 10); 
		else if ((asc >= 'a') && (asc <= 'f')) 
			bcd = (byte) (asc - 'a' + 10); 
		else 
			bcd = (byte) (asc - 48); 
		return bcd; 
	} 
	/** 
	 * BCD转字符串 
	 */ 
	public static String bcd2Str(byte[] bytes) { 
		char temp[] = new char[bytes.length * 2], val; 
 
		for (int i = 0; i < bytes.length; i++) { 
			val = (char) (((bytes[i] & 0xf0) >> 4) & 0x0f); 
			temp[i * 2] = (char) (val > 9 ? val + 'A' - 10 : val + '0'); 
 
			val = (char) (bytes[i] & 0x0f); 
			temp[i * 2 + 1] = (char) (val > 9 ? val + 'A' - 10 : val + '0'); 
		} 
		return new String(temp); 
	} 
	/** 
	 * 拆分字符串 
	 */ 
	public static String[] splitString(String string, int len) { 
		int x = string.length() / len; 
		int y = string.length() % len; 
		int z = 0; 
		if (y != 0) { 
			z = 1; 
		} 
		String[] strings = new String[x + z]; 
		String str = ""; 
		for (int i=0; i<x+z; i++) { 
			if (i==x+z-1 && y!=0) { 
				str = string.substring(i*len, i*len+y); 
			}else{ 
				str = string.substring(i*len, i*len+len); 
			} 
			strings[i] = str; 
		} 
		return strings; 
	} 
	/** 
	 *拆分数组  
	 */ 
	public static byte[][] splitArray(byte[] data,int len){ 
		int x = data.length / len; 
		int y = data.length % len; 
		int z = 0; 
		if(y!=0){ 
			z = 1; 
		} 
		byte[][] arrays = new byte[x+z][]; 
		byte[] arr; 
		for(int i=0; i<x+z; i++){ 
			arr = new byte[len]; 
			if(i==x+z-1 && y!=0){ 
				System.arraycopy(data, i*len, arr, 0, y); 
			}else{ 
				System.arraycopy(data, i*len, arr, 0, len); 
			} 
			arrays[i] = arr; 
		} 
		return arrays; 
	} 
} 
 
 

用法：

public static void main(String[] args) throws Exception { 
        // TODO Auto-generated method stub 
        HashMap<String, Object> map = RSAUtils.getKeys(); 
        //生成公钥和私钥 
        RSAPublicKey publicKey = (RSAPublicKey) map.get("public"); 
        RSAPrivateKey privateKey = (RSAPrivateKey) map.get("private"); 
          
        //模 
        String modulus = publicKey.getModulus().toString(); 
        //公钥指数 
        String public_exponent = publicKey.getPublicExponent().toString(); 
        //私钥指数 
        String private_exponent = privateKey.getPrivateExponent().toString(); 
        //明文 
        String ming = "123456789"; 
        //使用模和指数生成公钥和私钥 
        RSAPublicKey pubKey = RSAUtils.getPublicKey(modulus, public_exponent); 
        RSAPrivateKey priKey = RSAUtils.getPrivateKey(modulus, private_exponent); 
        //加密后的密文 
        String mi = RSAUtils.encryptByPublicKey(ming, pubKey); 
        System.err.println(mi); 
        //解密后的明文 
        ming = RSAUtils.decryptByPrivateKey(mi, priKey); 
        System.err.println(ming); 
    }